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Tuesday, May 29, 2012

ANAL CONES! Diadematid sea urchin mysteries!

Echinothrix from Lembeh Strait Photo (above) by Efdixon

Another day when pictures say more than words! What is an anal cone???

The anal cone is the weird, prominent bulb-shaped bit (its white in the species below) that is sitting on the top of the test (i.e., the body) in sea urchins of the family Diadematidae, which are well-known for their big long sharp spines....

But what function does it serve??
The Anal cone seemingly falls into the "poorly understood" category but I did find some explanations..

Another peculiarity of this family is that there is an elongated anal cone or sac which is commonly inflated like a small balloon in the centre of the upper side. This may gently roll around its attachment and is believed to have a respiratory function".

As in Diadema antillarum, the anal cone enables the animal to eject feces away from the body.

So here's a diversity of anal cones from various diadematid urchins! If they are for ejecting feces then these are some of the most aesthetically pleasing feces ejecting structures that I've seen among animals!

I believe this is Echinothrix from Hawaii
Photo above by JLambus

Astropyga from Sulawasi (photo below by pauldub)

Astropyga from Indonesia

Photo above by PacificKlaus

Another by PacificKlaus. Looks to be Echinothrix? from Okinawa, Japan

Astropyga from Lembeh, Indonesia

Photo above by Christian Loader

Another by Christian Loader. Maybe Echinothrix from Lembeh,

From Echinotrhix calamaris from Papua New Guinea. Photo below by jabaezam

Diadema? from tropical Atlantic
Photo above by marcsdad50

Echinothrix from Sulawasi (photo below by fisheyedave aka David Cropp)

About Me

I pursue starfish related adventure around the world with a critical eye and an appreciation for weirdness.
Support has been courtesy of the National Science Foundation but the views and opinions presented herein are mine and do not reflect the opinions of them or any affiliated institutions.
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